configure-swap: Always use dd and limit swap size to 1024MB

A recent kernel update in Fedora has highlighted that fallocate produced
swap files on ext4 partions are no longer accepted by swapon:

swapon failed if the swap file is created by fallocate in ext4 partition
https://bugzilla.redhat.com/show_bug.cgi?id=1827115

This change assumes that all distros will eventually encounter this and
removes the fallocate task from the role and defaults to using dd. As
this is considerably slower the overall size of the swap file is reduced
to 1024MB.

Change-Id: I5ce9064a5546d85ab6f41c4e60aa56fa56ff47c1

roles/configure-swap/defaults/main.yaml

@@ -1,2 +1,2 @@
 # Default swap partition/file size, in MiB
-configure_swap_size: 8192
+configure_swap_size: 1024

roles/configure-swap/tasks/root.yaml

@@ -20,21 +20,12 @@
 # Note, we don't use a sparse device to avoid wedging when disk space
 # and memory are both unavailable.
 
-# Cannot fallocate on filesystems like XFS, so use slower dd
-- name: Create swap backing file for non-EXT fs
-  when: '"ext" not in root_filesystem'
+- name: Create swap backing file
   become: yes
   command: dd if=/dev/zero of=/root/swapfile bs=1M count={{ swap_required }}
   args:
     creates: /root/swapfile
 
-- name: Create sparse swap backing file for EXT fs
-  when: '"ext" in root_filesystem'
-  become: yes
-  command: fallocate -l {{ swap_required }}M /root/swapfile
-  args:
-    creates: /root/swapfile
-
 - name: Ensure swapfile perms
   become: yes
   file: